dtls.c, netq.c: consider 32bit time overflow.

Fixes issue: #125

Signed-off-by: Achim Kraus <[email protected]>

dtls.c

@@ -4702,7 +4702,8 @@ dtls_check_retransmit(dtls_context_t *context, clock_time_t *next) {
   netq_t *node = netq_head(&context->sendqueue);
 
   dtls_ticks(&now);
-  while (node && node->t <= now) {
+  // comparison considering 32bit overflow
+  while (node && DTLS_IS_BEFORE_TIME(node->t, now)) {
     netq_pop_first(&context->sendqueue);
     dtls_retransmit(context, node);
     node = netq_head(&context->sendqueue);

dtls_time.h

@@ -51,6 +51,7 @@
 #endif
 
 typedef uint64_t clock_time_t;
+
 #else /* WITH_CONTIKI || RIOT_VERSION */
 
 #ifdef HAVE_TIME_H
@@ -62,6 +63,7 @@ typedef uint64_t clock_time_t;
 #endif
 
 typedef uint32_t clock_time_t;
+
 #endif /* WITH_CONTIKI || RIOT_VERSION */
 
 typedef clock_time_t dtls_tick_t;
@@ -73,6 +75,11 @@ typedef clock_time_t dtls_tick_t;
 void dtls_clock_init(void);
 void dtls_ticks(dtls_tick_t *t);
 
+// see https://godbolt.org/z/YchexKaeT
+#define DTLS_OFFSET_TIME (((clock_time_t)~0) >> 1)
+/** Checks if A is before (or equal) B. Considers 32 bit time overflow */
+#define DTLS_IS_BEFORE_TIME(A, B) ((DTLS_OFFSET_TIME + (B)-(A)) >= DTLS_OFFSET_TIME)
+
 /** @} */
 
 #endif /* _DTLS_DTLS_TIME_H_ */

netq.c

@@ -93,7 +93,8 @@ netq_insert_node(netq_t **queue, netq_t *node) {
   assert(node);
 
   p = *queue;
-  while(p && p->t <= node->t) {
+  // comparison considering 32bit overflow
+  while(p && DTLS_IS_BEFORE_TIME(p->t, node->t)) {
     assert(p != node);
     if (p == node)
       return 0;